Hit detection in direct-fire or small-arms simulators

ABSTRACT

A hit detection system including: a simulated weapon, a laser attached to the simulated weapon, a full screen projector projecting an image on a screen, a screen for target depiction and making a laser footprint visible to a hit-detection camera, at least a first hit detection camera being a high precision camera that is capable of detecting a laser footprint and generating hit detection data, a simulation computer in operative connection with the full screen projector and the hit detection camera, a link between a trigger on the simulated weapon and the first hit detection camera, a data storage means for storing hit detection data generated by the first hit detection camera, so that, in use, when a trigger on the simulated weapon is pulled to activate the laser a laser footprint is projected onto the screen and at the same time the hit detection camera takes an image of the laser footprint on the screen.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improvement to marksmanship training devices for assisting in firearms training.

In particular, the invention relates to improving the timing accuracy of the hit detection process used in the marksmanship training devices.

2. Description of the Related Art

Since human aiming involves continuous movement, improving the timing accuracy of the detection process is essential to the provision of feedback for aiming (and hence marksmanship) training

The last couple of decades have seen enormous strides in the development of video projectors and cameras. Cameras in particular have reduced in both size and cost, to the point where cameras have completely solid-state image sensors and hence very compact electronics.

Conventional video cameras have a number of limitations for use in hit-detection systems for simulation and in particular, for the function of hit-detection in small-arms simulators.

A typical indoor small-arms simulation system is shown in FIG. 1.

Components of such systems include: (1) a simulated rifle, hand gun, artillery or other weapon that normally ejects a projectile; (2) a sighting system that may be telescopic, but could be simpler (such as a sight on the end of a rifle) or more sophisticated (such as a head up display for tracking multiple targets); (3) a laser attached or embedded in some part of the simulated weapon, either generating a continuous beam for continuous tracking, or controlled by a trigger; (4) a projector that generates a computer controlled image on the screen; (5) a camera that views the whole screen; (6) the screen upon which images are projected and from which laser strikes are detected by the camera (5); (7) a target that can be projected anywhere on the screen, this may be a bulls-eye or other type of target used for marksmanship training, or could be a moving target; (8) the bright signature area generated by the laser; (9) the area of the screen viewed through the simulated weapon sight; and (10) the computer (or computers) controlling the weapons and effects simulation.

Referring to FIG. 1, when the trigger on the simulated weapon (1) is pulled the computer can use the location of the detected aim-point on the screen as part of the computation of the flight of a simulated projectile.

The advantage of these types of simulators is that they use no ammunition, are not dependent on weather conditions and can be used at any time of the day or night. Therefore, these devices are quite attractive propositions for low-cost training, or even training in places where access to live-ranges is not practical or possible, such as on board submarines.

One problem with such ‘indoor’ simulation systems is the difficulty in detecting the location of the centre of the laser spot to an accuracy that correlates to the real world. Since it is common for marksmen to aim at targets that are hundreds or even thousands of metres away, and typical indoor simulators are only tens of metres long then the tolerance within which the laser strike must be detected in a simulator is much tighter than that encountered in the real world.

For example a marksman who is aiming to get a shot within 100 mm of a point on a target at a range of 100 metres requires the simulator hit detection system to resolve between laser positions less than 10 mm apart on the simulator screen if the screen is 10 metres from the firing point (derived by using similar triangles).

In addition to the spatial tolerance requirement is the temporal accuracy requirement. No marksman can hold a gun or rifle completely stationary. Human muscles have tremors and humans must continue to breathe. Hence the marksman must pull the trigger smoothly so as not to jolt the rifle out of position. In addition the timing of the trigger movement must be such that the rifle, breathing and trigger pull all coincide at the point in time when the rifle is aimed at the desired point.

Humans can be very precise regarding timing of actions, with skilled humans able to time muscle movements to an accuracy of a few milliseconds. Thus, the hit detection system must be able to detect the laser footprint at a precise time and this is just as critical as the fine tolerances required for spatial location. That is, the aim point must be located accurately at the precise moment of the pull of the trigger so as to provide useful feedback for the human to develop marksmanship skills.

Current marksmanship simulators have three possible deficiencies, each of which contribute to an overall problem for hit detection: low-cost solid-state lasers produce low-frequency pulses of light; conventional video cameras refresh the detected scene at slow rates; and the simulation computers, laser pulses and video cameras all update asynchronously.

Conventional Video Cameras

To keep simulator costs down and reduce the requirement for specially manufactured video computer cards, the current generation of small-arms simulators use commonly available video cameras. These cameras typically refresh the whole image at 30 Hz. The video signal generated by such cameras may be either non-interlaced at 30 Hz, or interlaced where odd and even frames are refreshed alternately at 30 Hz. That is, the even lines of the image are typically refreshed in 1/60^(th) of a second then the odd lines of the image are refreshed in the next 1/60^(th) of a second. Interlaced video cameras require two scans to completely refresh the image so a complete image is built up over 1/30^(th) of a second.

Pulsed Lasers

Most low-cost solid-state lasers that have a high degree of brightness (visible or infra-red) are typically operated in a pulsed mode—the light beam alternates between on and off. For a given brightness level, pulsing the laser reduces the overall power consumption and heat dissipation requirements, as well as reducing the energy in the light, making the laser safer to use without eye-protection. Typical pulse rates may be in the order of 10 Hz to 20 Hz.

Asynchronous Components

Marksmanship simulators built from commercial-off-the-shelf components typically run those components in an asynchronous manner. This reduces development costs and complexity of the overall simulation system. It is possible that a simulator may comprise a mix of synchronous and asynchronous components, where for example there may be some synchronization between a laser pulse and trigger pull but no synchronization between other components.

Given that humans can control muscle movements to a precision of several milliseconds, the problem with asynchronous systems occurs when the processes run at frequencies where the total time delays are random with variations significantly greater than several milliseconds. Hit detection systems in simulators operate in the infra-red spectrum so as to be invisible to the human eye. Therefore the human cannot compensate for any random delay occurring from the hit-detection system.

To illustrate this effect consider the example in FIG. 2. The figure shows time plotted on the horizontal axis along the bottom, and an example of the processes at work in a laser-based hit-detection system above the line. The top line shows the trigger, the middle line shows the state of the laser pulse and the bottom row shows the state of the hit detection camera.

Referring to FIG. 2, the detection camera happens to switch to light detection mode just before the laser asynchronously pulses on, and the trigger happens to be pulled while the laser is on. In this case the detection latency is relatively small purely by chance.

Similarly, referring to FIG. 3, the detection camera happens to switch on and the laser asynchronously happens to pulse on. However, in this case, the laser pulses off, and the trigger is pulled just after the laser pulses on. In this case a detection will not occur until the laser pulses on. Alternatively a detection could be retrospectively be determined by using the last previous pulse. Either way, there is a potentially significant random error in determining where the laser was actually pointed at the time the of the trigger pull.

BRIEF SUMMARY OF THE INVENTION

It is an object of the invention to increase the timing accuracy of hit detection systems used in marksmanship training devices.

It is a further object of the current invention to provide a hit detection system for a marksmanship training device that ensures the laser footprint is located as close as possible in time to the actual moment of the trigger pull.

It is yet a further object of the invention to provide a hit detection process that is synchronous.

It is an object of the present invention to overcome, or at least substantially ameliorate, the disadvantages and shortcomings of the prior art.

Other objects and advantages of the present invention will become apparent from the following description, taking in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed.

According to the present invention, although this should not be seen as limiting the invention in any way, there is provided a marksmanship simulator including a weapon capable of firing a laser, a screen for projecting images thereon and for receiving a laser strike from the weapon, a first hit detection system for registering a laser strike on the screen, a first projector for projecting a background image and a target image on the screen.

In preference, there is provided a hit detection system in which the frequencies of all the asynchronous processes are increased so that the delay is below the performance threshold for humans.

In a further form of the invention, there is provided a method of improving the timing of a hit detection system, the method including the steps of increasing the frequencies of the all the asynchronous processes so that the variability of the delay is below the performance threshold for humans.

In preference, the frequencies will be greater than approximately 400 Hz.

In preference, these frequencies will be greater than approximately 1000 Hz

In a further form of the invention, there is provided a hit detection system for a marksmanship training device in which the regular laser pulsing system is disabled and a single short period laser pulse is generated upon pulling the trigger of a simulated weapon.

In a further form of the invention there is provided a hit detection system for a marksmanship training device, including a weapon capable of firing a laser, a screen for projecting images thereon and for receiving a laser strike from the weapon, a first hit detection system for registering a laser strike on the screen, a first projector for projecting a background image and a target image on the screen, in which a trigger on a simulated weapon is restricted to be activated at a rate less than or equal to a frame rate of a camera used to detect a hit.

In a further form of the invention there is provided a hit detection system, which includes a continuous wave laser, rather than a pulsed laser.

In preference, the system further includes a high-speed camera to detect the laser spot provided by a simulated weapon.

In a further form of the invention there is provided a hit detection system, which includes a pulsed laser to take advantage of the brighter reference point.

In preference, the system further includes a circuit that generates a steady stream of low frequency pulses for continuous tracking.

In preference, the system includes a second camera the second camera synchronized to take a high-speed image of the screen when the trigger is pulled.

In preference, a shutter speed of the second camera is long enough to capture the short duration phase of the laser pulse.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example, an employment of the invention is described more fully hereinafter with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a prior art system;

FIG. 2 is a diagram showing the processes at work in a laser based hit detection system;

FIG. 3 displays the situation when the processes are out of synchrony;

FIG. 4 is a schematic diagram of an embodiment of the current invention of continuous tracking with pulsed laser system;

FIG. 5 is a schematic diagram of an embodiment of the current invention referred to as trigger-laser synchronization.

DETAILED DESCRIPTION OF THE INVENTION

The present invention allows for the following to improve the problems associated with hit detection in marksmanship training devices, including increasing the frequencies of all the asynchronous processes so that the variability of the delay is below the performance thresholds for the human; or making the hit detection process synchronous.

Increase Detection Frequency

In this embodiment of the invention the simulation processes are still asynchronous, but the cycle times in all processes must be shortened so that the total random delay time is so small as to be negligible, compared to the human thresholds. Since expert human performance requires muscle coordination within a few milliseconds of precision, it is recommended that frequencies will need to be of the order of 400 Hz, and possibly greater than 1 kHz would be preferred. So if a pulsed laser is used, the pulsing must have a period of no more than a few milliseconds.

Alternatively the mark-space ratio of the laser pulses (the ratio of “on” to “off” time) must be such that the off time is no more than a few milliseconds in each cycle and the camera must have a shutter speed of no more than a few milliseconds, and the frequency of recording the scene must be of the order of 400 Hz or greater. The trigger pull time must also be polled at a similar rate (i.e. 400 Hz or greater), and the simulation computer must be able to detect a trigger pull and generate a recoil to the accuracy of several milliseconds. The end effect is that the cumulative random variation in delay, because of the asynchronous connection of processes, should be no greater than 5 to 10 milliseconds. This embodiment requires a video camera that operates at a very high rate. Such cameras can be expensive, and the simulation computer will have to cope with much larger amounts of data.

Synchronization

An alternative embodiment of the invention is to synchronize key parts of the simulation process.

Simple Laser-Trigger Synchronization

Synchronization can be achieved by disabling any regular laser pulsing and generate a single, very short period, laser pulse whenever the trigger is pulled. As long as the trigger is not allowed to be pulled successively at a rate greater than the frame rate of the camera then each video frame in the camera can contain no more than a single laser footprint, and then it is guaranteed that the laser footprint coincides with the aim-point of the rifle at the moment of the trigger pull.

Continuous Tracking with a Continuous Laser

The previous proposed implementation is relatively simple in terms of locating the aim-point. It can use conventional readily available commercial video cameras. However, it does not allow for continuous tracking of the aim point since only a single high precision laser pulse is generated which a relatively slow video camera can capture. A refinement allowing for continuous tracking is to use a continuous wave laser instead of a pulsed laser. A conventional video camera can be used for the purposes of tracking the laser to provide a low-precision plot of the laser footprint. This is similar to the current systems except that a continuous laser is required. But this alone does not enable high precision hit detection in time nor will it enable high precision spatial detection.

To solve these problems created by use of a continuous laser a high speed camera is also required. A high-speed camera is added to this system to detect the laser spot accurately relative to the point in time of the trigger pull. Referring to FIG. 4, (1) is the simulated weapon; (2) is used for sighting the target; (3) is the continuous laser attached to the simulated weapon; (4) is the full screen projector and (5) is the conventional video camera for continuous laser tracking; (6) is the screen used for the target depiction and making the laser footprint visible to the hit-detection cameras; (7) is the representation of the target on the screen; (8) is the laser footprint on the screen; (9) is the region detected by the high-precision camera (11); and (13) is a direct link between the trigger and camera (11) that bypasses the simulation computer (10). The reason for bypassing the simulation computer is so as to eliminate any delays inherent in the computer system. Although it is possible to have the simulation computer running at a high rate, bypassing the computer avoids the need for such high computational speeds, enabling the computer to be run in a conventional manner at lower iteration rates.

In the system as described in FIG. 4, the key element is the high speed link (13), which on trigger pull signals the high-speed camera to take an image of the simulation screen (6), and in particular a high resolution image of the target area (7) at the instant the trigger is pulled. This image can then be downloaded to the simulation computer at a later time for processing, analysis and feedback to the marksman or instructor. This process is then quite independent of the less accurate continuous laser detection processing that is going on in parallel which is mediated by the simulation computer (10). With this design, both the continuous tracking and high-speed hit detection processes can occur concurrently.

Continuous Tracking with Pulsed Laser

A refinement is to use a pulsed laser rather than a continuous laser. Pulsed lasers have the advantage that they can provide a brighter reference point than a continuous wave laser for the same power input. This will result in the laser footprint being both easier to detect and less hazardous to human eye-sight.

In this implementation, a circuit must generate a steady stream of low frequency pulses for continuous tracking The circuit must then provide for an additional pulse at the moment the trigger is pulled. To avoid problems associated with two laser pulses in a single video frame that would occur with a conventional video camera, a second camera is employed that is synchronized to take a single high-speed image of the screen when the trigger is pulled.

This is shown diagrammatically in FIGS. 4 and 5. FIG. 4 shows the same design elements as described in the previous section. Referring to FIG. 5, the regular stream of pulses for driving the laser is generated by a clock (1). The trigger contains a switch (2) and a circuit that generates a high-speed pulse when the trigger is pressed. The clock pulse and trigger pulse are combined by an ‘OR’ gate (so that either the trigger or the clock can produce a signal) and fed to a circuit (4) that generates a voltage (5) for illuminating the laser. The trigger signal (6) can also be sent as a trigger for a high speed camera (11) in FIG. 5.

In this design the camera shutter must be timed accurately to be open for a short period so as to ensure that the camera captures only the short-duration pulse of the laser, which is synchronized with the trigger pull.

1. Slow Camera Considerations

A commercially attractive possibility might be to use an inexpensive commercial-off-the-shelf camera system for this application. In the event that the camera or its associated componentry is unable to perform adequately due to slow image capture performance, this can be accommodated by having a two-stage trigger detection mechansim. The first stage of the trigger detection, either by first position switch or pressure sensor, prompts the camera and associated componentry to setup its internal configuration requirements for the image capture, while the second trigger point (the point of firing the simulated rifle) prompts the camera to capture the image.

2. Direct Trigger Link Connection

Synchronization of image capture with trigger activation can be achieved by a umber of methods, including, but not limited to: a) direct connection of trigger activation mechanism to camera input; b) direct connection of trigger activation mechanism to camera input through signal conditioning components; c) direct connection of trigger activation mechanism to camera input via the simulation computer yet independent of the simulation processing cycles; or d) direct connection of trigger activation mechanism to camera input by way of prioritized interruption of simulation processor cycles.

Various modifications may be made in details of design and construction [and process steps, parameters of operation etc.,] without departing from the scope and ambit of the invention. 

1. A hit detection system for hit detection in direct-fire or small-arms simulators comprising: a simulated weapon; a laser attached to said simulated weapon; a full screen projector projecting an image on a screen; a screen for target depiction and configured to make a laser footprint visible to a hit-detection camera; at least one first hit detection camera comprising a high precision camera that is capable of detecting a laser footprint and generating hit detection data; a simulation computer in operative connection with said full screen projector and said at least one first hit detection camera; a link between a trigger on said simulated weapon and said at least one first hit detection camera; a data storage object configured to store hit detection data generated by said at least one first hit detection camera; wherein when a trigger on said simulated weapon is pulled to activate said laser, a laser footprint is projected onto said screen and at a same time, said at least one first hit detection camera takes an image of said laser footprint on said screen.
 2. The hit detection system of claim 1, wherein said laser selected from the group consisting of continuous wave lasers and pulsed wave lasers.
 3. The hit detection system of claim 2, wherein when said laser is a pulsed laser illumination of said laser attached to said simulated weapon is as a result of said trigger being operatively connected to a switch and a circuit capable of generating a pulse that is subsequently fed to a circuit to generate a voltage configured to illuminate said laser so that activation of said trigger illuminates said laser.
 4. The hit detection system of claim 2, further comprising a video camera for continuous laser tracking
 5. The hit detection system of claim 4, wherein said at least one first hit detection camera is focused on only a target depicted on said screen.
 6. The hit detection system of claim 5, further comprising a target projector configured to project a target image onto said projector screen.
 7. The hit detection system of claim 4, further comprising a second hit detection camera synchronized to take an image of said screen when said trigger on said simulated weapon is pulled. 